4. On planet X, a cannon ball is fired straight upward. The positions of the ball at many times are listed below. Note that we have chosen up as the positive direction
Time (s) Height (m) Velocity (m/s)
0 0 0
1 17.5 17.5
2 30 15
3 37.5 12.5
4 37.5 10
5 30 7.5
6 17.5 5
7 2.5 2.5
8 0 0
a) Find the ball's average velocity during each adjacent time interval (between 0-1 s, 1-2 s, 2-3 s,..., 7-8 s) and enter the values into the table above.
b) What is the ball's average velocity (not speed) during its entire downwards descent?
c) What is the acceleration due to gravity on Planet X?
5. A commercial plane departs from New York City headed west toward Los Angeles at a speed of 850 km/h, while another plane simultaneously departs from Los Angeles headed for New York City with a tailwind at a speed of 950 km/h. The total distance between the cities is 4000 km.
a) How long after they depart will the two planes cross paths (in hours/minutes)?
b) How far from New York City will the two planes cross paths (in kilometers)?
6. A bolt comes loose from underneath a moving elevator that is 30 m above the bottom of the elevator shaft. The bolt reaches the bottom of the elevator shaft in 3.3 s.
a) What was the velocity of the elevator when the bolt came loose? Take the positive direction to be upward.
b) How fast was the bolt traveling once it hit the bottom of the elevator shaft?
7. The speed of light is approximately 3 x $10^8$ m/s. Convert this speed into kilometers per millisecond (km/ms).
7. A drone moves along a straight (1D) path with the velocities shown in the graph. Take "forward" to be the positive direction.
a) When is the drone moving forward? Backward? At rest?
b) What is the drone's displacement ($x_f - x_i$) in the first 2 seconds of its journey?
c) Bonus: What is the drone's displacement between $t = 2$ seconds and $t = 5$ seconds?
